The present invention relates to apparatus for feeding lifts of limp sheets. More particularly, the invention relates to apparatus for feeding lifts of paper sheets individually and successively from a stack of such sheets.
The sheets of the stack are limp flexible sheets of paper, or the like, of the type which would crumple, tear, and otherwise respond disadvantageously, if fed by a conventional mechanism.
Single sheets such as box blanks, single articles such as collapsed cartons, and single packages such as filled mailing envelopes, usually have enough resistance to bending to be fed individually from a magazine by a pusher blade, endless conveyor lugs, rotating friction wheels or movable suction cups. Double feeding in such apparatus is undesirable. In the present invention, however, the principal object is multiple feeding, since the apparatus is primarily intended for the purpose of simultaneously feeding a plurality of flimsy paper sheets in a unit, so that the unit may be passed through a punching, trimming, binding, stapling, stitching, gluing, or similar treatment.
The units or groups of limp, flexible, flimsy sheets are hereinafter referred to as "lifts". The sheets are usually of relatively small area such as are suitable for the printing and publishing art to be assembled into books, calendars, and the like. The lifts are not contained in a folded outer sheet, as in a signature, or bound at one edge, or provided with one extra long sheet usable for vacuum separation purposes, such packages being relatively easy to handle. The sheets in the lifts handled by the apparatus of the invention are identical in dimensions, unconnected, unbound, and without separators. This presents a difficult problem of accuracy in separation, segregation and withdrawal.
When the sheets are placed in an end feed magazine such as, for example, a gravity type, bottom feed hopper, the weight of the stack creates such friction that pusher blade feeds merely crumple the lift, vacuum separators are not effective and friction feeds affect only the bottom-most sheet and tend to crumple it.
The principal object of the invention is to provide apparatus for feeding lifts of limp sheets in which each successive lift in the magazine is mechanically and accurately separated from a stack thereof and is extracted from the magazine without crumpling of the sheets.
An object of the invention is to provide an apparatus for feeding limp sheet lifts in which each successive lift in the magazine is accurately and rapidly separated from the stack, and bodily rectilinearly moved out of the magazine.
Another object of the invention is to provide an automatic feeder capable of handling a large number of limp sheets per hour without danger of damaging the same and without danger of jamming of the feeder.
Still another object of the invention is to provide apparatus for depositing individual and successive lifts of limp paper sheets on a feed conveyor of an automatic punching, trimming, binding, stapling, stitching, gluing, or the like, device, the sheets in each lift being free of damage.
Yet another object of the invention is to provide apparatus of simple structure, which is inexpensive in manufacture and operation for feeding lifts of limp sheets.
Another object of the invention is to provide apparatus for feeding lifts of limp sheets, which apparatus is operable by one or two attendants, requires very little maintenance and is used with facility and convenience.
Still another object of the invention is to provide apparatus of simple structure for feeding lifts of limp sheets with rapidity, efficiency, effectiveness and reliability, without damage to the sheets.